Hi fitzage,
How are you setting up the sub-domains? If they are sub-folders of your main domain, you can place a copy of your main index.php file into the sub-folders for each sub-domain. Once you have those copies in place, you can use distinct global variables easily.
I’ve used the strategy outlined by Made by Hippo.
For example, you can then set each sub-domain’s site_url variable:
--- <a href="http://www.domain.com">http://www.domain.com</a> ---
$assign_to_config['site_url'] = 'http://www.domain.com/';
--- secondary domain/index.php ---
$assign_to_config['site_url'] = 'http://sub.domain.com/';
etc…
Allong with those config items, you can assign sub-domain specific global variables like so:
--- <a href="http://www.domain.com">http://www.domain.com</a> ---
$assign_to_config['global_vars'] = array(
"en"=>"English",
"my-other-variable" => "my-other-value"
); // This array must be associative
--- secondary domain/index.php ---
$assign_to_config['global_vars'] = array(
"fr"=>"French"
"my-other-french-variable" => "my-other-french-value"
); // This array must be associative
Let me know if you have any other questions.
Cheers,